This invention relates to a system for sharing data among storage systems in data processing systems or the like, and more particularly to a method of sharing data in a computer system which has a data storage subsystem with a plurality of interfaces.
“Downsizing” or causing an open system such as a personal computer (PC) or a workstation to carry out operations which were handled by a mainframe, has become an extensively adopted practice in recent years. Because a large quantity of information from past operations is stored in a mainframe, however, there is a demand for accessing that accumulated information from a small computer such as a PC.
The supplement Mainframe '98 (p. 214) to Nikkei Computer, a magazine published by Nikkei BP, carries an article on a case of composite configuration of a mainframe and an open system for a computer system used in corporate offices. In the computer system the article describes, the mainframe processes sales information, and the resulting accumulated data are collected and transferred once a day to a computer on the open system side via a network. This allows the user to refer to the data on the computer on the open system side. This arrangement enables data on core operations handled by the mainframe to be accessed from the open system. During such an access in this system, the current operation handled by the mainframe is suspended, and all the data are copied via the network. The greater the quantity of data handled, the longer the time required for copying. This results in heavier loads on host computer and the network, which may cause interruption in operations.
One solution to this problem is accessing a single disk unit (volume) by a plurality of host computers. Japanese Published Unexamined Patent Application No. 9-258908 discloses a disk apparatus having a plurality of interfaces and a method by which such a disk apparatus is accessed by host computers connected to the plurality of interfaces. According to this technique, copying of data between systems is dispensed with, and the load on host computer can be reduced accordingly.